In a conventional sewing machine, a plurality of threading portions such as a thread tension regulator, check spring and thread take-up is threaded sequentially in a predetermined route with a needle thread supplied from the thread spool. The needle thread ultimately threads an eye of a sewing needle attached to a needle bar, whereafter the needle thread is placed in condition to carry out a sewing operation. Such sewing machine is generally threaded manually by the user, whereby the plurality of threading portions is threaded with the needle thread.
In contrast, a sewing machine provided with an automatic threading device that sequentially threads the plurality of threading portions is also available nowadays. In such a sewing machine, the needle thread supplied from the thread spool is set in a predetermined threading route in advance. Then, the needle thread set in the threading route is caught by a hook and carried to the plurality of threading portions to thread the same.
For example, an automatic threading device disclosed in JP-B-H02-14866 (hereinafter referred to as patent reference 1) includes a thread holding member; an operating lever having the thread holding member pivoted to the distal end thereof and a base end thereof pivoted to a sewing machine frame; a thread carrier member having a lock member in the distal end thereof and having a base end thereof pivoted to a sewing machine frame; and an operating portion. A thread tension regulator is provided in the upper portion of a sewing machine arm. The automatic threading device threads the threading portions with a needle thread as follows. First, threading portions in the extremity of a thread take-up, the thread holding member, and the lock member of the thread carrier member are arranged to project above the sewing machine arm by the user. Then, a thread tension regulator, the threading portion of the thread take-up, and the thread holding member are threaded sequentially with the needle thread supplied from the thread spool to place the sewing machine in condition for a sewing operation.
By operating the operating portion from this state, the operating lever and the thread carrier member are rotated, whereby the thread holding member holding the needle thread is lowered to the proximity of the sewing needle. Then, a threading hook of the automatic threading device threads the eye of the sewing needle with the needle thread. Also, the lock portion of the thread carrier member is lowered, engaging the needle thread therewith. The needle thread is thereafter brought into engagement with a check spring disposed inside the sewing machine arm. In instances where automatic threading of plurality of threading portions is not possible due to failure of the automatic threading device, manual threading is required on the part of the user.
However, the patent reference 1 does not disclose any threading technique allowing manual threading of the plurality of threading portions with the needle thread. More specifically, the type of sewing machine disclosed in patent reference 1 has threading portions such as the check spring, the thread take-up, and the thread tension discs housed inside the sewing machine; hence, substantial effort is required on the part of the user to manually thread the threading portions with the needle thread. One possible solution to such problem may be removing the sewing machine cover to provide access to the threading portions. More specifically, the front cover covering the threading portions such as the check spring, the thread take-up and the thread tension discs may be removed to enable manual threading of the same.
However, the sewing machine having the automatic threading device disclosed in patent reference 1 is not designed to manually thread the plurality of threading portions with the needle thread. Thus, if the automatic threading device breaks down, it becomes extremely difficult to thread the plurality of threading portions. Thus, the ease and reliability of threading the plurality of threading portions is suspended until the automatic threading device is repaired, impairing the quality of sewing work.
In view of the above problem, the sewing machine covers that cover the front side of the check spring, the thread take-up, and the thread tension discs may be removed to enable manual threading of the same. However, manual threading requires time consuming user intervention such as detachment and reattachment of the covers. Also, removing the covers does not guarantee easy and reliable threading of the plurality of threading portions. Moreover, removing the covers and activating the exposed thread take-up and needle bar may have unexpected negative impact on the sewing process.